Scion xB Forum banner

1 - 20 of 46 Posts

·
Registered
Joined
·
279 Posts
Discussion Starter #1
Just bought this XB 3 weeks ago (used, 70k miles). So I love this car and just want this ordeal to get fixed and be over with it. I bought it as a family vehicle for my wife and 1 year old. Couple days after I bought it, I got the three stooges light. I figured it was a loose gas cap, reset it by disconnecting the battery and it did nothing. The lights would appear and disappear on their own every day. I finally went to Aamco today (free check engine light scans) and the code P0012 showed up (cam over-retard). From there I went to the dealership and they diagnosed the car for about 5 hours. They called me back and said it was pin pointed to the VVTI control actuator assembly (+$500!!). Now, I bought this vehicle from a dealership and it comes with a 90 day, 3000 mile limited powertrain warranty (i am still within the parameters). The dealership is now saying that my issue is an electrical one and not covered under that limited warranty. Does anyone know if this is bull? Can anyone show me a link or something in writing that clearly states that this problem is something that can be covered under that warranty? And finally, how the heck does this sort of thing happen? Thanks in advance for reading and any help.
 

·
RS4 #303
Joined
·
4,900 Posts
All the repair/wiring diagrams and the TSB's and codes can be found here. Technical Service Bulletins are like a recall and should be fixed by the dealer.
Scion Document List
 

·
06.5 TCM
Joined
·
10,027 Posts
I meant the one you got from the dealer that sold you the car. Any words in the policy on what's covered?
 

·
Registered
Joined
·
279 Posts
Discussion Starter #6 (Edited)
Hey pch I would like to try that fix from the link you sent but no idea where those parts are. Do you have a picture or diagram.

As far as the 90 day 3000 mile powertrain, here is what it says : engine- all internally lubricated parts including crankshaft, main bearings, rods, pistons, rings, camshaft, timing gears, belt, valves, lifters, pushrods, springs, oil pump, heads, block.

Transmission- torque converter, vacuum modulator, internal electric control units, over drive units, shift forks and cases only if damaged by the failure of an internally lubricated part listed above.
 

·
06.5 TCM
Joined
·
10,027 Posts
Camshaft actuator should fall under "timing gears".

The part that dealeship says needs to be replaced is attached to the intake camshaft. On the pic it's the one of two top chain driven gears (the one on the right and has 4 bolts in it)



Other parts that may be affecting the operation of the actuator are the solenoid valve and the filter behind it. They are located near the alternator and can be accesed without taking the the side engine cover off.

 

·
Registered
Joined
·
130 Posts
My background is push rods and carburetors. Can someone explain how this variable cam timing component works? I understand it adjusts the length of time the intakes are open. My question is HOW does it do it?
I mean that timing chain is locked to the crank and exhaust cam. How can the intake spin at a different speed?
What actual adjusts this change in speed?
 

·
06.5 TCM
Joined
·
10,027 Posts
The lenght of time and speed are not changed. VVT changes when the intake valves start to open by advancing the intake camshaft. Kind of like spark advance in the distributor. It's done by regulation how much oil pressure is allowed inside the actuator. At high engine speed the intake cam is advanced and at idle it's not. So you can have more valve overlap at high RPM and still have good idle and low emissions.
 

·
4 Time Scion Owner
Joined
·
9,475 Posts
^yup, it's the same way a vtec honda motor works... But doesn't VVT-i isn't a performance upgrade with the stock configuration. It's more of a gas saver. Now with a camcon you can adjust the vvti settings and gain i think 5-10hp just from that alone. Then if you alter fuel curve and tune and such, probably if done right, 10-15hp, 20hp at the very most.
 

·
Registered
Joined
·
130 Posts
So it is like a torque converter in an automatic transmission?
At idle the adjuster/camshaft has some slip, so doesn't open right away.
then when you rev up the oil pressure is increased and this locks the adjuster tighter to the actual cam shaft which caused the valves to open sooner?
But wouldn't this also cause the intake valves to stay open later?
 

·
06.5 TCM
Joined
·
10,027 Posts
It's more like an adjustable camshaft gear. The simple mechanical one looks like this:



And VVT actuator is controlled by how much oil is pumped inside:



So the slip is there only for a very limited angle during adjustment. Otherwise it's basically always locked and even if there is no oil pressure it will simply be fixed at the most "retarded" (zero advance) position. More oil expands the inner chambers and camshaft advances relative to the chain or a belt sprocket. Computer continiously looks at how much advance there is and regulates the oil flow with the Oil control valve.
This system is very sensitive to oil contamination. So clean good quality oil with right viscosity is very important. The contriller has wearable parts and seals inside that will fail at some point. All you can do is to make them last longer.
 

·
Registered
Joined
·
4 Posts
Old thread, but I'll give it a shot--
My 05 xB falls within the TSB & way beyond 60K, P0012 appearing regularly since 35K....I'm a very conservative driver, get excellent mileage, so no drivability problems for me. Always a problem getting yearly inspection, as it won't pass with MIL on, so must wait for MIL to go out, then wait for "Ready" on ScanGuage, and quickly get inspected before MIL comes on again.
Is there a way to shunt the signal to the ECM which tells it the camshaft is over-retarded? What type of logic is involved here? Can it be as simple as grounding or opening a circuit so the P0012 is never indicated?
 

·
06.5 TCM
Joined
·
10,027 Posts
The logic is that ECU looks at the signal from the Camshaft Postion Sensor and it has to be within 5 degrees of the target advance angle. Since it varies all the time you can't substitute it with a fixed value.
 

Attachments

·
Registered
Joined
·
4 Posts
Thanks, PCH, for your response. What I was hoping to shunt was the signal that was generated that would place the P0012 code into memory, and light the MIL. That would involve a "switch" ie., "off" meaning "no P0012 code into memory" and "on" meaning "put code P0012 into memory". I have a feeling this logic takes place within the heart of a particular i/c chip within the ECU itself and so an intimate knowledge of the actual chip involved would be necessary.....inasmuch as I would not want to disable any other codes from being generated, it sounds high near impossible to isolate this one code for elimination.
 
1 - 20 of 46 Posts
Top